Species composition or biodiversity? What drives benthic communities resistance to thermal stress?

Type:

Master Thesis subject (30 ECTS)

programme:

EMBC+

The responses of coastal marine environments to climate change are of particular interest, due to their sensitivity and rapid response to anthropogenic changes, but also to their socio-economical and ecological importance. The increased frequency of climatological extremes and variability are among the main consequences of climate change, which in exposed coastal ecosystems may have major impacts on communities or even lead to biodiversity loss.
The aim of this thesis is to investigate whether the tolerance of a community to episodic temperature stress and to increased daily temperature fluctuations depends more on its species composition, and hence on the presence of tolerant species in all trophic levels and functions, or whether the biodiversity of the community itself relates with its stress resistance. Specifically, the following hypothesis will be tested using microcosm experiments with natural communities: The resistance to episodic temperature extremes and increased fluctuations depends on species composition rather than on species diversity. Community resistance can be assessed from, among others, total abundance, biomass and trophic complexity (e.g. food chain length).
Sediments will be collected from the intertidal zone of a dissipative beach at the Belgian part of the North Sea, which is naturally exposed to temperature fluctuations at various temporal scales (from hours to seasons). However, the degree of thermal stress co-varies with intertidal position. Hence, we will collect communities from three sampling sites across the intertidal beach gradient of environmental conditions and exposure to thermal stress. Sediments with natural communities selected from each of the three sites will be subjected to normal temperature regimes vs regimes with a thermal stress episode lasting from days to weeks. Nematode functional diversity will be assessed using both classical (feeding type diversity, life history, individual size and biomass distributions) and novel (e.g food-web complexity based on stable isotope measurements) approaches.